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How to Recommend Power Supply Unit

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  • Power Supplies
  • Components
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June 7, 2012 7:49:57 AM

Hey Everyone,

I have some of questions.

I wanted to know when you recommend a power supply unit do you read benchmarks of watts used in a particular component? For example CPU uses 128W when overclocked, and the GPU uses 300W when on full load.

Or do you use the stated wattage by the manufacturer?
For example, at Intel.com they listed the i5-2500k for Max TDP of 95W. Or newegg states that a graphics card needs at least 500W.

Also, do you use a power supply unit for full system load or have some overhead?
For example, a fully customized system is rated for 500W. Do you buy the exact watts or give some overhead (525W) or go higher such as 600W?

Last question, is it better for the Power Supply Unit to be loaded at 50% of it's capacity versus 85% capacity? Will it decrease the life or performance of the PSU? (and no it's not about efficiency levels such 80 PLUS bronze, gold, etc)

Thanks for any replies :) 

More about : recommend power supply unit

June 7, 2012 8:17:59 AM

fantastik250 said:
Hey Everyone,

I have a some of questions.

I wanted to know when you recommend a power supply unit do you read benchmarks of watts used in a particular component? For example CPU uses 128W when overclocked, and the GPU uses 300W when on full load.

Or do you use the stated wattage by the manufacturer?
For example, at Intel.com they listed the i5-2500k for Max TDP of 95W. Or newegg states that a graphics card needs at least 500W.

Also, do you use a power supply unit for full system load or have some overhead?
For example, a fully customized system is rated for 500W. Do you buy the exact watts or give some overhead (525W) or go higher such as 600W?

Last question, is it better for the Power Supply Unit to be loaded at 50% of it's capacity versus 85% capacity? Will it decrease the life or performance of the PSU? (and no it's not about efficiency levels such 80 PLUS bronze, gold, etc)

Thanks for any replies :) 

First go by what your components are drawing not by the company standards, when they say the graphics card needs 500w, they mean the gpu and the entire computer system, based on normal power draws of components, and yes, overhead is good, not to much, and your efficiency ranking goes into that, like if you are only using 40% of the maximum wattage of a psu, the efficiency rating is much lower. if your maximum power-draw is 500w lets say...buy one 750w no more. and remember, electrical components only draw as much power as they need, so if you buy a 1000w psu it will still only draw the 500w, well if its 80 plus gold...then it will draw like 555w+ the extra because you are running @ 50% load, so it will end up drawing 575-600w...god don't know what i just typed, its 4 in the morning lol

**edit** psu's can typically also draw more power then what their labels say, this is typically 10-30% more**
a b ) Power supply
June 7, 2012 8:18:08 AM

as to your question about recommending power supplies usually if the person is OCing his cpu I give 200w for the cpu factor in, and for gpu it depends if its a single 6pin then around 100w if its 8pin then around 200w. this is just guesstimation. and yes it is better to be in the 40-70% range if at all possible.

I always always ALWAYS give a system about a bit extra from the 70% mark at the very least. (if the system uses 300w I recommend a 550w)

(heck I still have trouble recommending a 7750 for a 300w psu.

@l1nks dude... thats a whole mess of words im not dissecting at 1 in the morning <3

If its a high-end card I weigh the benefits of going xfire/sli if its a low-end gaming rig (say an i3 + 7750) I don't use less then 500w (no real benefit) this is only on builds.
Related resources
June 7, 2012 8:21:18 AM

mouse24 said:
as to your question about recommending power supplies usually if the person is OCing his cpu I give 200w for the cpu factor in, and for gpu it depends if its a single 6pin then around 100w if its 8pin then around 200w. this is just guesstimation. and yes it is better to be in the 40-70% range if at all possible.

I always always ALWAYS give a system about a bit extra from the 70% mark at the very least. (if the system uses 300w I recommend a 550w atleast)

(heck I still have trouble recommending a 7750 for a 300w psu.

@l1nks dude... thats a whole mess of words im not dissecting at 1 in the morning <3


yes well, its 4 in the morning here and i was just reading down his questions and drawing from my knowledge lol
June 7, 2012 8:21:25 AM

mouse24 said:
as to your question about recommending power supplies usually if the person is OCing his cpu I give 200w for the cpu factor in, and for gpu it depends if its a single 6pin then around 100w if its 8pin then around 200w. this is just guesstimation. and yes it is better to be in the 40-70% range if at all possible.

I always always ALWAYS give a system about a bit extra from the 70% mark at the very least. (if the system uses 300w I recommend a 550w atleast)

(heck I still have trouble recommending a 7750 for a 300w psu.

@l1nks dude... thats a whole mess of words im not dissecting at 1 in the morning <3


Same here lol, about the 300w PSU situation.
June 7, 2012 8:22:52 AM

l1nks said:
First go by what your components are drawing not by the company standards, when they say the graphics card needs 500w, they mean the gpu and the entire computer system, based on normal power draws of components, and yes, overhead is good, not to much, and your efficiency ranking goes into that, like if you are only using 40% of the maximum wattage of a psu, the efficiency rating is much lower. if your maximum power-draw is 500w lets say...buy one 750w no more. and remember, electrical components only draw as much power as they need, so if you buy a 1000w psu it will still only draw the 500w, well if its 80 plus gold...then it will draw like 555w+ the extra because you are running @ 50% load, so it will end up drawing 575-600w...god don't know what i just typed, its 4 in the morning lol

**edit** psu's can typically also draw more power then what their labels say, this is typically 10-30% more**


Oh now that's a good bit of information to know. I didn't know that the PSU would actually draw more power from itself by more than what the manufacturer states.
June 7, 2012 8:23:37 AM

fantastik250 said:
Same here lol, about the 300w PSU situation.


yeah i know it just shows my thought process on the screen and it's too late to structure my sentences when you do read it though, it answers most of your questions i hope lol
June 7, 2012 8:24:26 AM

fantastik250 said:
Oh now that's a good bit of information to know. I didn't know that the PSU would actually draw more power from itself by more than what the manufacturer states.


yeah but be careful, its like overclocking, if you do it too much it puts the psu at risk
June 7, 2012 8:25:17 AM

l1nks said:
yeah i know it just shows my thought process on the screen and it's too late to structure my sentences when you do read it though, it answers most of your questions i hope lol


oh no no, I wasn't lol'ing at your post. I was actually laughing and agreeing at the fact that it's quite difficult to recommend someone a 7750 with a 300W psu.
a b ) Power supply
June 7, 2012 8:25:21 AM

fantastik250 said:
Oh now that's a good bit of information to know. I didn't know that the PSU would actually draw more power from itself by more than what the manufacturer states.


Well, not really. I mean some can but its definately not designed to do that all the time, its more used in voltage spikes etc (ie when you are just starting up say a water cooling pump)

The good ones are rated at continuous wattage buuuut I still wouldn't do any more than 400w on a 500w continuous psu.

Let me go into detail a bit more here.

There are more things then simply wattage to take into consideration, such as load line calibration, ripple, how well it stands up to sporratic voltages/dirty power, how it adapts to UPS back up systems (some power supplies just don't like them at all) etc etc etc.

The most common issue I find you have to look out for is, what wires are on what rails, say you want to connect 2 6990s on a 1000w psu (for a bitcoin farm or something) and you have 3 rails, rated at 27a each (for a max combined wattage of 972) and lets just say the psu manufacturer decided to put 3 8pins on 1 rail along with the 4+4pin for the cpu, then the other rail is populated by an additional 8pin and the last rail is just full of molexs for whatever reason, chances are you are going to have to use molex connectors instead of some of the 8 pins on the cpu rail.

(320w per rail, cpu takes 125w alone. + 3 8pins use 360 for a total of 485w.... and thats a bit overboard.)

I doubt any sane psu manufacturer would do something remotely like this but... useful info nonetheless
June 7, 2012 8:31:40 AM

mouse24 said:
Well, not really. I mean some can but its definately not designed to do that all the time, its more used in voltage spikes etc (ie when you are just starting up say a water cooling pump)

The good ones are rated at continuous wattage buuuut I still wouldn't do any more than 400w on a 500w continuous psu.


i wasn't recommending he run a system like that, it was just a little bit more information about psu's i threw in there, and i ran one like that for a couple weeks before i upgraded the psu
June 7, 2012 8:34:29 AM

To help you better understand what you are asking about and to help you learn enough to understand what the "real world vs the Marketing strategy", PLEASE read through these links...this will help you understand just what a power supply is AND what really matters when looking to purchase a "quality" psu.

Read ALL these....it will be very "powerful" stuff that will make sense of what you need.

http://www.tomshardware.com/forum/324368-28-computer-po...

http://www.jonnyguru.com/forums/showthread.php?t=1036

http://www.hardwaresecrets.com/article/181

http://www.techsupportforum.com/forums/f210/power-suppl...

These pages illuminate what you should really be considering and what to look for on the Labels of PSU's.

Hope this helps you in deciding what you need and why you need it!

Good Luck my friend:) 

!